The present invention relates to a vehicle anti-roll system, and more particularly, to a hydraulically-operated anti-roll system which limits the amount of tilt induced in a vehicle to counteract turn-induced roll.
For the purpose of establishing the general environment in which the invention operates, it is asserted that a vehicle such as an automobile consists of a body, four tires, two front and two rear, a frame with axles for mounting the front and rear wheels, and a suspension for connecting the vehicle body to the axles.
When a vehicle turns, the suspension permits the vehicle body to rotate slightly about its longitudinal axis in response to the rolling force exerted on the body during the turn. Typically, vehicle passengers experience this effect as a tilt of the vehicle body, with the side of the body on the outside of the curve being relatively lower than the side of the body on the inside. Further, the vehicle body tends to pitch forward so that the front of the body is relatively lower than the rear. The pitch and roll combine to incline the vehicle body toward the front corner on the outside of the turn.
Anti-roll systems are known in the art which counteract vehicle roll by providing a lifting force acting between the vehicle body and suspension on the outside of the curve or a vehicle lowering force acting between the body and suspension on the inside turn side of the vehicle. Some anti-roll systems in the art provide complementary lifting and lowering forces simultaneously.
U.S. Pat. No. 3,752,497 of Enke et al illustrates an anti-roll system in which complementary lifting and lowering forces are applied. In the Enke et al patent, two sets of complementary lifting and lowering forces are provided, one set to the front wheels, and one set to the rear.
In U.S. Pat. No. 3,820,812 of Stubbs, an anti-roll system includes two separate assemblies, each working on the front and rear axles on a respective side of a vehicle. Each assembly provides a lifting or lowering force to its respective side, without reference to the action of the other assembly.
U.S. Pat. No. 3,885,809 of Pitcher illustrates an anti-roll system in which two separate correction units on opposite sides of the vehicle provide lifting and lowering forces to counteract roll. The Pitcher anti-roll system also includes a lift limitation assembly interconnected with the anti-roll system components and serving the rear of the vehicle.
U.S. Pat. No. 4,345,661 of Nishikawa provides a correcting force to one side of a vehicle to counteract turn-induced roll.
My U.S. Pat. No. No. 4,589,678 operates on the front wheels to counteract roll. It also provides limitation of front wheel correction by means of a piston controlled hydraulic line operating between a hydraulic reservoir and a cylinder and piston assembly.
All of these existing anti-roll systems utilize hydraulic circuitry and components for generating lifting and lowering forces. In each case, an element corresponding to a cylinder and piston assembly is positioned at a vehicle wheel and acts between the wheel and the vehicle body by moving a piston within a cylinder. Movement of the piston toward the top of the cylinder compresses the assembly's longitudinal profile and exerts a lowering force by drawing together the vehicle body and the wheel. Movement of the piston downwardly in the cylinder spreads the assembly longitudinally and exerts an erecting force which separates the body and the wheel. The operations of a plurality of such assemblies are coordinated by hydraulic circuitry. The circuitry reacts to roll forces by developing hydraulic signals in the form of pressurized hydraulic fluid, and delivering those signals in appropriate configurations to the cylinder and piston assemblies. None of the instances cited above provides a closed hydraulic circuit which connects all four front and rear cylinder and piston assemblies into an integrated anti-roll system in which all of the parts act cooperatively and in response to a single hydraulic signal. Beyond not teaching this combination, these references further do not suggest the joinder of such an anti-roll system with a tilt limitation feature which limits the degree of correcting tilt developed at all four wheels to counteract vehicle rolling. Neither do these references illustrate shock absorbency internal to the hydraulic components of an anti-roll system.